Bug 1267936 - make a stronger assertion to catch that MediaDecoder is created when MediaShutdownManager::Shutdown() begins. r=jya.

MozReview-Commit-ID: K3OdjMFGEUF

dom/media/MediaShutdownManager.cpp

@@ -49,7 +49,7 @@ MediaShutdownManager::Instance()
 void
 MediaShutdownManager::EnsureCorrectShutdownObserverState()
 {
-  MOZ_ASSERT(!mIsDoingXPCOMShutDown);
+  MOZ_DIAGNOSTIC_ASSERT(!mIsDoingXPCOMShutDown);
   bool needShutdownObserver = mDecoders.Count() > 0;
   if (needShutdownObserver != mIsObservingShutdown) {
     mIsObservingShutdown = needShutdownObserver;